A bar code is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths, the bars and spaces having differing light reflecting characteristics. The pattern of the bars and spaces encode information. Bar code may be one dimensional (e.g., UPC bar code) or two dimensional (e.g., DataMatrix bar code). Systems that read, that is, image and decode bar codes employing imaging camera systems are typically referred to as imaging-based bar code readers or bar code scanners.
Imaging-based bar code readers may be portable or stationary. A portable bar code reader is one that is adapted to be held in a user's hand and moved with respect to a target indicia, such as a target bar code, to be read, that is, imaged and decoded. Stationary bar code readers are mounted in a fixed position, for example, relative to a point-of-sales counter. Target objects, e.g., a product package that includes a target bar code, are moved or swiped past one of the one or more transparent windows and thereby pass within a field of view of the stationary bar code readers. The bar code reader typically provides an audible and/or visual signal to indicate the target bar code has been successfully imaged and decoded.
A typical example where a stationary imaging-based bar code reader would be utilized includes a point of sale counter/cash register where customers pay for their purchases. The reader is typically enclosed in a housing that is installed in the counter and normally includes a vertically oriented transparent window and/or a horizontally oriented transparent window, either of which may be used for reading the target bar code affixed to the target object, i.e., the product or product packaging for the product having the target bar code imprinted or affixed to it. The sales person (or customer in the case of self-service check out) sequentially presents each target object's bar code either to the vertically oriented window or the horizontally oriented window, whichever is more convenient given the specific size and shape of the target object and the position of the bar code on the target object.
A stationary imaging-based bar code reader that has a plurality of imaging cameras can be referred to as a multi-camera imaging-based scanner or bar code reader. In a multi-camera imaging reader, each camera system typically is positioned behind one of the plurality of transparent windows such that it has a different field of view from every other camera system. While the fields of view may overlap to some degree, the effective or total field of view of the reader is increased by adding additional camera systems. Hence, the desirability of multi-camera readers as compared to single camera readers which have a smaller effective field of view and require presentation of a target bar code to the reader in a very limited orientation to obtain a successful, decodable image, that is, an image of the target bar code that is decodable.
U.S. Pat. No. 5,717,195 to Feng et al concerns an “Imaging Based Slot Datform Reader” having a mirror, camera assembly with photosensor array and a illumination system. The disclosure of this patent is incorporated herein by reference.
Barcode scanners using imagers have become common in many retail applications. In theory, an imaging barcode reader could capture an image of an item such as a screw, bolt, washer etc to identify the product. Merely capturing an image is not enough to allow the particular part to be identified. Identifying a screw requires a measurement of the length and diameter of the screw's threaded portion. The identification also requires thread pitch and an identification of the screw head. Both the shape and the size of the features must be obtained to accurately identify the screw. Similar measurements are needed to identify a bolt, washer, nail etc.
Some items sold in retail stores do not have labels bearing barcodes so they cannot be scanned at the cash register. Examples of such products are screws, nails, nuts and washers all of which can be purchased at home improvement stores. When these items are purchased the sales clerk must identify the item, typically by comparing it to a picture located near the cash register and then manually entering a SKU number via the cash register keyboard. This is time consuming and there is a good chance the wrong SKU number will be entered either because the wrong item is identified or the clerk makes an error in entering the SKU into the cash register. Other items such as fruit or vegetables are sold in supermarkets that do not have bar codes but may have identifying indicia which must be manually entered by the clerk.